redolog文件头简单探究
先切换:
SQL> select group#,status from v$log;
GROUP# STATUS
---------- ----------------
1 INACTIVE
2 CURRENT
3 INACTIVE
SQL> alter system archive log current;
System altered.
SQL> select group#,status from v$log;
GROUP# STATUS
---------- ----------------
1 INACTIVE
2 ACTIVE
3 CURRENT
SQL>
再进行dump:
SQL> alter system dump logfile '/u01/app/oracle/oradata/orcl/redo02.log';
System altered.
SQL>
然后再进行比较:
SQL> select group#,first_change# ,next_change# from v$log;
GROUP# FIRST_CHANGE# NEXT_CHANGE#
---------- ------------- ------------
1 1022213 1032521
2 1032521 1037135
3 1037135 2.8147E+14
SQL> select checkpoint_change# from v$database;
CHECKPOINT_CHANGE#
------------------
1037135
SQL>
看dump文件的头部:
DUMP OF REDO FROM FILE '/u01/app/oracle/oradata/orcl/redo02.log'
Opcodes *.*
RBAs: 0x000000.00000000.0000 thru 0xffffffff.ffffffff.ffff
SCNs: scn: 0x0000.00000000 thru scn: 0xffff.ffffffff
Times: creation thru eternity
FILE HEADER:
Compatibility Vsn = 186647552=0xb200400
Db ID=1369801323=0x51a5826b, Db Name='ORCL'
Activation ID=1369789803=0x51a5556b
Control Seq=816=0x330, File size=102400=0x19000
File Number=2, Blksiz=512, File Type=2 LOG
descrip:"Thread 0001, Seq# 0000000008, SCN 0x0000000fc149-0x0000000fd34f"
thread: 1 nab: 0xccad seq: 0x00000008 hws: 0x2 eot: 0 dis: 0
resetlogs count: 0x323036ef scn: 0x0000.000e2006 (925702)
prev resetlogs count: 0x3121c97a scn: 0x0000.00000001 (1)
Low scn: 0x0000.000fc149 (1032521) 04/14/2014 15:20:36
Next scn: 0x0000.000fd34f (1037135) 04/14/2014 17:27:22
Enabled scn: 0x0000.000e2006 (925702) 03/12/2014 14:36:31
Thread closed scn: 0x0000.000fc149 (1032521) 04/14/2014 15:20:36
...
fc149 16进制= 1032521
fd34f 16进制= 1037135